Air quality is subject to variability due to weather, dust, traffic and localized pollutant sources. Seasonal variations in pollen can trigger asthma and allergies in sensitive individuals. Similarly, exposure to high levels of coarse and fine particulate matter introduced from the outside can lead to respiratory irritation and has been associated with increases in lung cancer as well as cardiovascular disease and mortality. Carbon filters are designed to absorb such volatile pollutants and remove the largest particles, while media filters are meant to address smaller particles.